Optical waveguides – With splice – Fusion splicing
Reexamination Certificate
2002-06-06
2004-10-05
Glick, Edward J. (Department: 2882)
Optical waveguides
With splice
Fusion splicing
C385S097000, C385S098000
Reexamination Certificate
active
06799903
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber fusion splicer and an optical fiber fusion splicing method for fusion splicing two optical fibers of different mode field diameters using an electric arc discharge.
When structuring communication cable networks or manufacturing equipments using optical fibers, there are often instances where two optical fibers of mutually different mode field diameters are fusion spliced. In such a case, if an attempt is made to merely use an arc discharge fusion splicer to fusion splice these two optical fibers, a connection loss becomes larger than that of an instance where optical fibers of the same mode field diameters are connected to one another.
To address such an issue, in the state-of-the-art practice, various attempts have been made to connect two optical fibers of different mode field diameters to maintain the connection loss as low as possible. For instance, in an approach proposed in Japanese Patent Provisional Publication No. 2000-098171, when fusion splicing an optical fiber of a smaller mode field diameter on one hand and an optical fiber of a larger mode field diameter on the other hand, terminal ends of both the optical fibers are abutted to one another with abutted portions being fusion spliced using electric discharge heating and, thereafter, the electric discharge heating position is displaced from the abutted portions toward one of the optical fibers, of which mode field diameter is small, to apply additional electric discharge heating thereto in a reduced heating quantity to allow dopant of a core portion of the relevant optical fiber to be diffused for thereby permitting only the mode field diameter of the relevant optical fiber to be gradually enlarged in a lengthwise direction of the optical fiber.
Thus, by enlarging the mode field diameter of the relevant optical fiber of the smaller mode field diameter in a tapered shape, a substantial matching of mode field diameters of both the optical fibers at joint portions can be made, resulting in reduction of a connection loss. Also, the presence of an elongated tapered length enables connection of both the optical fibers with a limited increase in the connection loss that would be otherwise caused by a shortened tapered length, with a resultant further reduction in the connection loss.
Further, in Japanese Patent Provisional Publication No. 2000-275469, an alternative approach has been made in that, when establishing a matching of mode field diameters by applying additional electric discharge heating to an optical fiber of a small mode field diameter once fusion splicing operation has been conducted using an electric discharge heating, an attempt is made to obtain transmitted light images of the optical fibers after a fusion spliced condition, to estimate values of mode field diameters from brightness distribution curves and to estimate values of the mode field diameters of the optical fibers, one of which is applied with the additional heating using an estimated value for thereby observing a matching condition between the mode field diameters of both the optical fibers whereupon the additional heating is terminated when the matching condition is judged to fall in a sufficient range.
However, according to an aspect of the method proposed in Japanese Patent Provisional Publication No. 2000-098171, when fusion splicing the optical fibers of different mode field diameters, it is required to preliminarily find one of the two optical fibers, of which mode field diameter is small, and to set the optical fibers in fixed places. If such operation is wrongly carried out, then a reversed result appears, requiring nerves in fusion splicing operation.
With the approach proposed in Japanese Patent Provisional Publication No. 2000-275469, since the attempt is merely made to estimate the mode field diameters through image observations of the optical fibers to which the initial heating (fusion splicing heating) and the additional heating have been applied, there is a need for an operator to manually settle a travel distance in which the heating position is traveled toward the optical fiber of the smaller mode field diameter to be applied with the additional electric discharge heating, resulting in requirement not only in troublesome works but also in highly skilled experiences to achieve suitable settings with an inability in performing the splicing operation.
SUMMARY OF THE INVENTION
It is, therefore, a first object of the present invention to provide an improved optical fiber fusion splicer in which when splicing optical fibers of different mode field diameters, there is no need for an operator to set the optical fibers upon finding which optical fiber has a smaller mode field diameter and which is effective to automatically judge which settled optical fiber has the smaller mode field diameter to enable additional electric discharge heating to be applied to the relevant optical fiber of the smaller mode field diameter while automatically moving an electric discharge beam relative to the relevant optical fiber after electric discharge fusion heating.
It is a second object of the present invention to provide an improved optical fiber fusion splicer which when applying additional electric discharge heating to a relevant optical fiber while relatively moving an electric discharge beam thereto after fusion heating, enables a travel distance to be automatically optimized.
It is a third object of the present invention to provide an improved optical fiber fusion splicer which when applying additional electric discharge heating to a relevant optical fiber while causing an electric discharge beam to be relatively traveled after fusion splicing heating has been completed, enables a heating quantity to be automatically optimized.
It is a fourth object of the present invention to provide an optical fiber fusion splicing method in which when splicing optical fibers of different mode field diameters, there is no need for an operator to set the optical fibers upon finding one of the optical fibers, of which mode field diameter is small and in which judgment is automatically made to find one of the optical fibers settled, of which mode field diameter is small to enable additional electric discharge heating to be applied to the relevant optical fiber of the smaller mode field diameter and in such a way that a travel distance and a heating quantity are automatically optimized while automatically causing an electric discharge beam to be traveled relative to the relevant optical fiber after electric discharge fusion heating has been completed.
To address the above issues, according to a first aspect of the present invention, there is provided an optical fiber fusion splicer comprising an image pick up unit obtaining transmitted light images passing through side areas of abutted portions between two optical fibers of mutually different mode filed diameters, an image processing unit calculating mode field diameters of the respective optical fibers from brightness distributions of the images in terms of directions traverse to the optical fibers, an electric discharge heating unit applying electric discharge heating to the abutted portions with an electric arc discharge beam, a movable unit operative to move the electric arc discharge beam such that it travels relative to the abutted portions along an optical fiber axial direction, and a control unit controlling the electric discharge heating unit and the movable unit such that after conducting electric discharge fusion splicing heating to the abutted portions, a position of the electric arc discharge beam is traveled toward one of the optical fibers, of which mode field diameter is regarded to be small by the image processing unit, to apply additional electric discharge heating to the same to allow the mode field diameter of the relevant optical fiber to be enlarged.
Processing the transmitted light images due to lights passing through the side areas of the two optical fibers enables the respective mode field diameters to be calculat
Kawanishi Noriyuki
Kubo Toshiki
Saito Shigeru
Barber Therese
Fujikura Ltd.
Glick Edward J.
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